Numerous solid antiperspirant and/or deodorant compositions have been described in the chemical and cosmetic literature. These compositions generally are emulsion sticks or suspensoid sticks. Emulsion sticks contain a solution of the antiperspirant ingredient incorporated into the stick via an emulsion. Although emulsion sticks are desirable in certain respects, they tend to be unstable, exhibit tackiness, and leave a visible residue on the skin after use. Suspensoid sticks contain the powdered antiperspirant ingredient suspended in the stick without the use of water or an emulsion. While suspensoids have stability, they tend to leave a white chalky residue on the skin after application.
With respect to deodorant activity, sodium bicarbonate has long been recognized for its deodorant properties, and has commonly been used as a household deodorant. Plain powdered sodium bicarbonate, or sodium bicarbonate diluted with talc or other filler, has been used as an underarm deodorant as disclosed in U.S. Pat. No. 4,382,079. Other publications which describe cosmetic stick compositions containing a bicarbonate deodorant include U.S. Pat. No. 4,822,602 and U.S. Pat. No. 4,832,945.
However, the development of a practical and effective composition in cosmetic stick form which has a deodorization capacity, and which is capable of consumer acceptability, presents many factors which are unique. Because sodium and potassium bicarbonate have only limited solubility in water, alcohol and other solvents, the preparation of a composition suitable for dispensing in cosmetic stick form has involved many processing obstacles. In addition to the problem of limited solubility, sodium bicarbonate often is incompatible with other ingredients of conventional stick compositions. Also, the dimensional stability of the cosmetic stick containing sodium bicarbonate, and the esthetic appearance and the "feel" on the skin, are just a few of the additional difficulties encountered in the preparation of a low residue deodorant cosmetic stick product.
A recent trend is toward the development of cosmetic sticks which have light transmitting properties, i.e., the cosmetic sticks are translucent or transparent in light transmitting properties, and engender a perceived appearance of purity.
Cosmetic sticks which are soap-based and which have a content of sodium bicarbonate as a deodorant ingredient typically are opaque in appearance. U.S. Pat. No. 4,440,742 describes anhydrous and water-based deodorant cosmetic sticks which contain sodium bicarbonate, and which vary from opaque to transparent in appearance as determined by the proportions of sodium bicarbonate and water, in combination with other ingredients.
U.S. Pat. No. 5,424,070 describes a transparent solid stick composition containing ingredients such as propylene glycol, water, sodium stearate and Eumulgin L.
There are difficulties associated with the preparation of water-based cosmetic stick product which contain sodium bicarbonate as a deodorant ingredient. Thus, the transparency properties do not have long-term stability. Acceptable degrees of hardness and smoothness are not readily achieved, and an unpleasant cool-wetness is experienced when the cosmetic stick is applied to a skin surface.
There is continuing interest in the development of water-based deodorant cosmetic stick products which have a high degree of consumer acceptance.
Accordingly, it is an object of this invention to provide a cosmetic stick product which is a water-based composition having an effective deodorizing content of alkali metal bicarbonate salt.
It is another object of this invention to provide a bicarbonate salt-containing deodorant cosmetic stick product having stable transparency and affording a comfortable dry feel when applied to a skin surface.
Other objects and advantages of the present invention shall become apparent from the accompanying description and examples.